Logic 9 Are EXS Jam Pack 4 string files stereo?

I can't get them to change to mono no matter which of the many options I try. So I assume they must be stereo and that is why I can't load then into a mono software instr. channel strip without the strip changing to stereo, right?

That is indeed exactly the way it works. A Channel strip setting is a combination of instrument and plugins. If any plugin is either stereo or mono>stereo it will force the channel to be stereo, irrespective of wether the software instruments and its associated samples are mono or stereo.